Figure 3. Impact of confirmed autophagy inducers on RPE lipid metabolism. (A) Proposed model of RPE lipid handling. Lipid-rich shed OS are phagocytosed from the apical side and lipoprotein complexes are consumed from the basolateral side daily. Incomplete lipid degradation contributes to lipofuscin accumulation. With the remaining lipid load, we postulate that the RPE daily determines the balance between complete lipid degradation, as assessed by KB production, and secretion of lipid via lipoprotein particles, as assessed by apoE secretion. (B) KB production (as assessed by β-hydroxybutyrate, β-HB) in the presence of vehicle (DMSO) or confirmed autophagy inducers for 24 hours. β-HB is secreted almost exclusively into the apical supernate. Only FLBZ increased lipid degradation. Torin n=4, GSK n=7, FLBZ n=6, D4476 n=4. (C) Apolipoprotein secretion (as assessed by apoE) in the presence of vehicle (DMSO) or confirmed autophagy inducers for 24 hours. Both apical and basolateral media contain apoE. While increasing lipid degradation in (B), FLBZ also decreases secretion of drusen-promoting apolipoprotein. Apical: Torin n=4, GSK n=5, FLBZ n=11, D4476 n=4. Basal: Torin n=4, GSK n=5, FLBZ n=9, D4476 n=3. ns p > 0.05, *p < 0.05, **p < 0.01.